Some information about Grass

Grass is the common word that generally describes monocotyledonous green plants. The family Gramineae (Poaceae) are the "true grasses" and include most plants grown as grains, for pasture, and for lawns (turf). They include some more specialised crops such as lemongrass, as well as many ornamental plants. They also include plants often not recognized to be grasses, such as bamboos or some species of weeds called crab grass.

Grass-like plants are among the most versatile life forms. Plants having grass-like structures have existed for millions of years, providing fodder for Cretaceous dinosaurs, whose fossilized dung (coprolite) contains phytoliths of a variety of grasses that include the ancestors of rice and bamboo.[1] Grasses have adapted to conditions in lush rain forests, dry deserts, and cold mountain steppes, and are now the most widespread plant type.
Plants of this type were always important to humans. They were cultivated as food for domesticated animals for up to 10,000 years. (See grass fed beef.) They have been used for paper-making since at least 2400 BC. Now they provide the majority of food crops, and have many other uses, such as feeding animals, and for lawns. There are many minor uses, and grasses are familiar to most human cultures.
In some places, particularly in suburban areas in the United States and Canada, the maintenance of a grass lawn is a sign of a homeowner's responsibility to the overall appearance of their neighborhood. Many municipalities and homeowner's associations have rules about this. Some require lawns to be maintained to certain specifications, sanctioning those who allow the grass to grow too long. In communities with drought problems, watering of lawns may be restricted to certain times of day or days of the week.

Even more info:
+ Why the grass is green
+ How grass works